An intermolecular potential function for the methanol dimer from <i>a</i> <i>b</i> <i>i</i> <i>n</i> <i>i</i> <i>t</i> <i>i</i> <i>o</i> calculations

An intermolecular potential function for the methanol dimer has been derived from ab initio molecular orbital calculations with a minimal basis set (STO-3G). Dimerization energies for 270 orientations of the dimer chosen using the energy distributed random geometries method were fit to a 12-6-1 potential function. A five particle model was adopted for each monomer consisting of the oxygen atom with two pseudotone pairs, the hydroxyl hydrogen and the methyl group. The fit for bound geometries is excellent, while repulsive points are less well represented owing to the simple model for the methyl group. By analyzing accurate potential functions for the methane and water dimers, corrections for the methyl–methyl and oxygen–hydrogen dispersion interactions are estimated. The modified potential has proven successful in simulations of liquid methanol.